The present invention relates generally to tractor controls preventing engagement of a power-takeoff assembly when the engine speed exceeds a predetermined amount and, more particularly, to an interlock between the engine throttle and the power-takeoff engagement control to restrict engagement of the tractor power-takeoff.
An inherent problem with typical tractor power-takeoff drives on agricultural tractors is that the PTO clutch is vulnerable to operator abuse either by engaging the clutch to start the power-takeoff with the engine running at maximum speed and/or by the engagement of the clutch with a stalled output receiving the rotational power from the PTO. Current PTO control designs require the provision of a clutch with sufficient capacity to dissipate peak energies associated with a full stall and with full speed PTO clutch engagement. This requirement necessitates the specification of a clutch in the power-takeoff design which is much larger and more expensive than that required for normal, low-speed, moderate load, PTO engagements and continued operations.
It would be desirable to provide a means for limiting the engagement of the tractor power-takeoff so that the PTO clutch can only be engaged at times when the engine speed is at a reasonable level, thereby eliminating the need to an oversized clutch in the power-takeoff driveline. Since the energy absorbed by the PTO clutch is proportional to the square of the rotational input speed, limiting the input speed at which the clutch is to be engaged to two-thirds of the rated engine speed would result in the energy requirements of the PTO clutch to be reduced by a factor of greater than fifty percent. Accordingly, it would be desirable to provide a tractor control interlock preventing the engagement of the tractor power-takeoff when the speed of operation of the engine is greater than a reasonable, predetermined amount.